Switch off the unit, protect food, and use a coil-safe cleaner with a soft brush or low-pressure rinse. Keep water off fan motors, heaters and wiring, and make sure the drain can carry the water out. For heavily fouled coils, or when the housing needs to be opened, have a technician do it.
The evaporator sits in the warm, humid air of the box and collects a thin film of grease vapor, dust and food particles. The film reduces heat transfer, holds moisture, feeds mold and can make frost harder to melt. It is less obvious than a dirty condenser, so it often gets overlooked.
The evaporator housing contains fan motors, heater elements and sensors. Turn off and lock out the power before any cleaning near it. If you cannot reach the coil without removing covers, leave it to a technician.
Signs it needs cleaning
- A grey or greasy film on the fins.
- A musty smell near the housing.
- Frost that builds unevenly or lingers after defrost.
- Slow recovery after door openings.
- Mold in the drain pan.
What staff can do
- Power down. Use the disconnect and confirm the fans are still.
- Protect food. Move or cover product below the housing.
- Cover electrical parts. Use plastic sheeting to shield anything you cannot avoid.
- Vacuum loose dust. Use a soft brush attachment on the visible fins.
- Apply a coil-safe cleaner. Use one labeled for evaporators and food areas. Follow the dwell time.
- Rinse lightly. Use a low-pressure spray or damp cloths, and keep the water moving toward the pan.
- Check the drain. Pour a little water into the pan and confirm it drains.
- Dry and restart. Allow the coil to drip, then restore power and watch the fans.
What a technician does differently
- Opens the housing safely and cleans between fins and around fan blades.
- Uses proper coil cleaners and rinses so residue does not remain.
- Cleans the pan, drain and trap thoroughly.
- Checks the heaters, sensors and fan wiring for damage or corrosion.
- Looks for refrigerant leaks and oil stains while the coil is exposed.
What to avoid
- No pressure washers, which flatten fins.
- No strong acid or bleach on the coil.
- No scraping or chipping of ice or fins with tools.
- No spraying into fan motors or terminal boxes.
- No cleaning products that are not rated for food areas.
How often
For most kitchens, a look every month and a proper clean once or twice a year is reasonable. Boxes near a fryer or grill, or with heavy door traffic, may need more. Ask your technician to include evaporator cleaning in the annual visit. The maintenance checklist shows how it fits with other tasks.
Related: how to clean the condenser coil, freezing up and defrost repair, and smell and mold.
Questions about cleaning the evaporator
Can I clean it while the box is stocked?
It is safer to move or cover food. Cleaning warms the box and introduces water and cleaner.
Why is the coil clean but frost still builds?
Frost comes from moisture entering the box and from defrost problems, not only dirt. See the freezing up page.
What cleaner is safe?
Use one made for evaporator coils and rated for food areas, and follow the label. Ask a technician which they use.